Manufacture of sheet-iron



UNITED STATES PA ENT OFFICE IsAAo n. CRAIG, or CAMDEN, on-Io.

MANUFACTUREOF SHEET-IRON.-

SPECIFIGATION forming part of Letters Patent No. 280,799, dated July, 10, 1883, Application filed November 20,1882. (No model.)

To all whom it may concern:

. Be it known that I, IsAAo E. CRAIG, a citizen of the United States, residing at Camden, in the county of Preble and State of Ohio, have invented a certain new and useful Improvement in the Manufacture of Sheet-Iron,

increasing its capacity for receiving and its,

ability to retain a smooth and polished surface at a less expense than by the methods now in use for that purpose; and I do hereby declare that the following is a full, clear, and exact description of the invention, which will enable others skilled in the art to which it appertains to make and use the same.

Heretofore iron has been prepared for being polishedin sheets either by dissolving away the covering of oxide of iron, which forms on it While being rolled, by the use of acids, or else by restoring the iron contained in the coating of oxide to the metallic state by heat ing the sheets in packages with layers of powdered charcoal or some other form of combustible carbon to a sufficiently high temperature and for a sufficient length of time to pro duce the chemical change just named. In this invention I adopt the last-named of these two methods of cleaning the sheets; and the object of the invention is to leave the surface of the sheets, when cleaned in this manner, less porous and inclined to rust and more easily susceptible of a good and durable luster than they have heretofore been, and to this end my invention consists in associating with the com bustible carbon used in reviving the metal of the oxide on the sheets a suitable quantity of plumbago, which I find, when the oxide of iron has parted with its oxygen to the combustible carbon, replaces the oxygen in combination with the metal, unites with the revived porous iron much more readily and in larger proportions than combustible carbon does, thereby lessening its porosity and giving it a very highly carbonaceous character, which is favorable to the reception of a polish.

' To carry myinvention into effect I make use of a good quality of sheet-iron having its surface well oxidized by exposure to air while being rolled or annealed. Both surfaces of each sheet I moisten with a mixture of water and plumbago, made in the proportion of. four pounds of plumbago to one gallon of water,

I applying the mixture with a large brush, and

i then cover the sheets with some form of combustible carbon. I prefer fine'charcoal-powder applied through a wire sieve to a thickness not much less than that of the sheet. An-

other sheet moistened with the same mixture is then laid on this, and its upper surface treated with charcoal in like manner as the first. This operation is repeated until the pile of sheets is as large as the capacity of the furnace will admit or convenience of handling allow. The pile is then wrapped about by other sheets of iron, to. be held in place by stout wire, and placed in an ordinary reverberatory furnace. It is then raised to a bright red but not to awelding heat, and maintained at this temperature for about two hours. The package is then removed from the furnace, and before being allowed to cool is opened and the sheets taken apart while still red-hot, so that their surfaces may slightly reoxidize. Each sheet when cool, and before the application of any mechanical force which would tend to incorporate with or attach to the sheets the carbonaceous dust not already taken up by chemical action, should be carefully cleansed from adhering charcoal and plumbago by brushing, or, as I think best, by thoroughly washing with clean water and bristle brushes. They are now ready to be done up in packages and finished under the hammer, or, as I think less desirable, by either burnishing or rolling. This operation is conducted as follows: From five to twenty sheets (I prefer ten or twelve) are heated to cherry redness or slightly higher in the ordinary sheet or annealing furnace, with a heavier piece of sheet-iron or plate-iron on each side of the package, and hammered under a steam-hammer until it is reduced to a black heat, then reheated and hammered again, until by successive heats and hammering it is found to have sufficient luster. It is then, without further annealing, ready to be shorn of irregular edges and done up for the market. When they are designed to be polished by rolling, they should be deoxidized and carbonized when two or three times thicker than they are intended to finish, so that they may, by loose rolling to further reduce their thickness, also acquire the desired luster.

Sheet-iron prepared by this method for being polished has the following advantages over that prepared by other methods now practiced:

It has less tendency to rust from exposure to air and moisture, and by reason of the plu mbago uniting with the revived iron in much larger proportions than carbon exists in steel, and also in much larger proportions than combustible carbon will do under similar circumstances, a surface compound is produced which I find to have greater facility of polish and power of retaining the luster than can be obtained without the use of plumbago in the manner described.

Having fully described my invention, what I desire to claim and secure byLetters Patent As an improvement in the manufacture of sheet-iron, the process herein set forth, consisting in applying to the surface of the sheets, in addition to the combustible carbon used to deoxidize them, a suitable quantity of plumbago to chemically unite with the iron of the oxide on their surface and replace, in combination with the metal of the oxide, the oxygen which is "yielded up to the combustible earbon; then, after properly inclosing the sheets to prevent circulation of air among them heating and maintaining them at a high red heat until the chemical change above named has taken place, and reoxidizing them by exposure to air while hot; then cleansing them from adhering carbon before making use of any mechanical force which would tend to fix or attach the same to the sheets, and finally p0lishing by rolling or hannnering in the usual manner. I

ISAAC E. CRAIG. Witnesses:

O. 1. BROWN, (3. POTTENGER. 

